Macrophage subpopulations and RPE elimination in the pathogenesis of experimental autoimmune pigment epithelial protein-induced uveitis (EAPU)

Experimental autoimmune pigment epithelial protein-induced uveitis (EAPU) is a new type of disease that destroys the retinal pigment epithelium (RPE), and exhibits a hitherto unknown form of progressive chorioretinal dystrophy in which neuroretinal inflammatory foci are absent. The present study was aimed at studying the expression of adhesion molecules, and the kinetics of the appearance of the main types of macrophages and other intraocular immunocompetent cell populations in the various stages of this disease. EAPU was evoked in Lewis rats by immunization with the membrane protein from bovine RPE cells containing PEP-65 as main constituent. In the uvea, increased expression of intercellular adhesion molecule-1, of class II major histocompatibility complex antigen, and of ED2 macrophage reactivity were observed closely before the onset of EAPU. Expression of these reactivities was also slightly elevated by injections of the applied adjuvants alone. The onset of EAPU was mainly characterized by initial uveal infiltrations of ED1+ macrophages and a minor population of CD4 T cells, and an increase in ED3, ED7 and perivascular ED2 reactive macrophages. This was followed by the development of focal accumulations of ED1+ cells at both sides of the Bruch's membrane-RPE layer (Dálen-Fuchs nodules) which was permeated and disintegrated at these sites. The outer choroidal layer, the anterior iridal surface, and the base of the ciliary body more frequently contained active inflammatory cells than the other uveal areas. Lymphoid cells were found scattered through the uvea, aqueous and vitreous. The sites of increased activity of ED2+ and ED3+ cells in the uvea were rather similar to those of ED1 macrophages in the various stages of EAPU. Starting from multiple foci, the process of the formation of plaque-shaped cell accumulations in severe EAPU progressed along the RPE and exhibited a chronic character. The results of this study show that ED1+, ED2+, ED3+ and ED7+ subpopulations of macrophages are actively involved in an immunopathological process in which the RPE is the target. The thickening of the plaque-shaped cell accumulations stops if the integrity of all RPE cells at that site has been affected. We postulate that this is the result of antigen elimination while additional influence of the abrogation of RPE cytokine production is presumed.

The effects of prostaglandins E2 and F2 alpha on porcine ciliary muscle cells in culture

The purpose of this work is to investigate the effect of prostaglandins (PGs) on the contraction of ciliary muscle cells. It has been proposed that PGs induce relaxation of ciliary muscle and facilitate uveoscleral outflow, and reduce intraocular pressure (IOP). The ocular response to PGs is complicated because the relative contributions of uveoscleral flow and the conventional outflow to lowering IOP and the type of PG receptors associated with ciliary muscle may vary depending on animal species. In order to obtain insights into prostaglandin receptors of ciliary muscle, ciliary muscle cells from porcine eye were grown in culture and characterized immunocytochemically with antibodies against smooth muscle-alpha-actin and PGE2 receptor subtypes. As in ciliary muscle tissues, positive immunostaining for alpha-actin and EP2 and EP3 subtypes was observed in cultured cells. Time-dependent contraction of cultured cells induced by 10(-4) M carbachol was recorded by taking sequential photographs and analyzed. Using this assay method, the effect of prostaglandins E2 and F2 alpha to inhibit the carbachol-induced contraction was studied. PGE2 showed potent inhibition of cell contraction; 10(-7) approximately 10(-8) M PGE2 inhibited 50% of full contraction in 15 min. PGF2 alpha at 10(-4) M neither caused cell contraction by itself nor blocked carbachol-induced contraction. The EP2 agonist 11-deoxy-16, 16-dimethyl PGE2 at 10(-4) M inhibited cell contraction but the EP3 agonist sulprostone had no effect. Dibutyryl cAMP at 3 x 10(-5) M inhibited contraction by 50%. In the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), less than 10(-7) M dibutyryl cAMP caused 50% inhibition. In support of the cAMP effect, the addition of 10(-4) M PGE2 to cultured cells in the presence of indomethacin and IBMX was shown to cause an 80% increase in intracellular cAMP concentration compared with the basal (i.e. unstimulated) level of cAMP. Stimulation of cells with 10(-4) M PGF2 alpha caused no increase in cellular cAMP. These results indicate that PGE2 receptor EP2 subtype, but not PGF2 alpha receptor, is involved in the inhibition (hence relaxation by inference) of carbachol-induced porcine ciliary muscle cell contraction. It awaits further studies to determine whether cultured ciliary muscle cells of other species respond similarly to different PGs.

[The resistance to drainage of the aqueous humor]

The presence of the evacuation paths of aqueous humor at the level of the camerular angle makes it play an important role on open angle glaucoma pathology. The fundamental element in the evacuation of aqueous humor is the endothelial cell, who has a main contribution to the routing of aqueous humor using the phenomenon called micropinocytosis. With the age the number of endothelial cells diminishes, their function reduces and an atypical collagen appears, together with the thickness of the basal membrane, the agglutination of the trabecular blades and Schlemm channel collapse. The fact is that the raise of the evacuation resistance in open angle glaucoma must not be interpreted mechanically; a research from a biochemical and molecular point of view must be completed.

Studies of human uveal melanocytes in vitro: isolation, purification and cultivation of human uveal melanocytes

PURPOSE

To develop the methods for isolation and cultivation of human uveal melanocytes (UM) from adult donor eyes.

METHODS

After removal of the pigment epithelium, the uvea was pretreated in trypsin solution at 4 degrees C overnight, incubated at 37 degrees C with trypsin for 1 hr, then incubated with collagenase for 3 hr. Released cells were collected each hour during the incubation and cultured with F12 medium supplemented with fetal bovine serum, basic fibroblast growth factor, isobutylmethylxanthine and cholera toxin. Contaminant cells were eliminated by adding a selective cytotoxic agent, geneticin, when necessary.

RESULTS

These methods provide pure melanocyte cultures with high cell yields, good viability, and rapid growth rates. UM isolated and maintained using these methods can be passaged 23 times for a period of 7 mo for more than 35 population doublings. This is comparable to results obtained with cultured neonatal dermal melanocytes and exceeds results obtained with adult dermal melanocytes cultured in media supplemented with phorbol ester, isobutylmethylxanthine, and cholera toxin.

CONCLUSION

A method for isolation and cultivation of UM has been developed that yields satisfactory results. Cultured UM may be useful in in vitro studies of UM physiology and may allow development of in vitro models of the pathogenesis of uveal malignant melanoma.

Studies of human uveal melanocytes in vitro: growth regulation of cultured human uveal melanocytes

PURPOSE

The authors studied the growth requirements and growth regulation of cultured human adult uveal melanocytes (UM).

METHODS

The effect of various mitogens and growth factors on the growth of UM were tested separately or combined on cultured UM in multiwell plates.

RESULTS

Basic fibroblast growth factor (bFGF) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) stimulate the growth of UM. Without these agents, the UM did not grow or survive. A cyclic adenosine monophosphate (cAMP) stimulator, such as isobutylmethylxanthine or cholera toxin, stimulated growth in the presence of bFGF. Fetal bovine serum (FBS) is also required for growth. In its absence, UM did not grow, even in the presence of bFGF and cAMP stimulators. Other substances, such as epidermal growth factor, acidic FGF, nerve growth factor, and platelet-derived growth factor had no stimulating effects on the growth of UM.

CONCLUSIONS

Three classes of agents are required for the growth of UM in vitro: bFGF or TPA, a cAMP stimulator, and FBS. Adult human UM cultured in medium containing all these agents grew well and could be passaged for many generations.

Reduction by OK-432 of the monolayer contact-mediated inhibition of human natural killer cell activity

In the present study we investigated the effect of OK-432, a streptococcus preparation, on the contact-mediated inhibition of human NK activity by primary cultures of monolayer cells. Either peripheral blood lymphocytes (PBL) or large granular lymphocytes (LGL) were incubated (2 x 10(6) cells/ml, total volume 2 ml) on confluent monolayer cells (uvea-derived fibroblasts, uvea-derived melanoma cells, or renal carcinoma cells) for 18 h in 24-well plates, washed twice, and tested for cytotoxicity against K562, a human myelogenous leukemia cell line, in a 4 h 51Cr-release assay. After contact with monolayer cells, NK activity of both PBL and LGL was significantly reduced. When these effector cells were preincubated with 0.1 U/ml of OK-432 for 18 h and then tested for the sensitivity to contact-mediated inhibition, the inhibition was significantly reduced. The pretreatment of monolayer cells with OK-432 or the addition of OK-432 into the coculture wells (of effector cells and monolayer cells) also significantly reduced the contact-mediated inhibition. Moreover, OK-432 (0.1 U/ml) reestablished the inhibited NK activity of PBL. These results suggest that OK-432 might enable NK cells to escape from the contact-mediated inhibition by monolayer cells and thus provide an additional potential mechanism for the observed clinical effectiveness of OK-432 reported by many groups.

HLA antigens in ocular tissues. III. Antigen presentation by gamma interferon-treated cultured uveal cells

In previous studies we have shown that normal human uveal cells, with the exception of vascular endothelium, do not express class I or class II HLA antigens in vivo. Class I antigens are induced in vitro by a variety of cytokines, while class II antigens are only induced by gamma interferon. In this study we examine the capacity of cultured uveal cells, rendered class II HLA antigen positive by gamma interferon, to present antigen to T cells. Cultured uveal cells were found to present antigen (tetanus toxoid, PPD, and Candida albicans) to T cells, but only when they were pretreated with gamma interferon. This function of uveal cells was antigen specific and MHC restricted and was blocked by class II-specific monoclonal antibodies, indicating the crucial role of class II HLA antigens in antigen presentation.

Expression of HLA antigens on the human uvea

We examined the expression of HLA antigens on post-mortem human uveal tissues and on cultured uveal cells. There was no in vivo expression of class I or class II antigens in these tissues, except for the blood vessel endothelium which expressed class I but not class II antigens. Tissue cultured uveal cells were found to express class I antigens. The effect of interferon-alpha and interferon-gamma on the in vitro expression of these antigens was examined. Class I HLA antigen expression was enhanced by both interferon-alpha and interferon-gamma, while class II HLA antigens were induced on up to 100% of cultured cells, but only by interferon-gamma. These findings are discussed in their relation to immune mechanisms occurring in ocular inflammatory disorders.

The melanocyte. Its structure, function, and subpopulations in skin, eyes, and hair

I would like to stress that there seem to be three subpopulations of neural crest-derived melanocytes in the body that can be functionally and morphologically distinguished: the cutaneous melanocytes, which continuously synthesize small melanosomes to be transferred to keratinocytes; the uveal melanocytes, which synthesize larger melanosomes for only a short while to be retained by this melanogenically dormant cell; and the hair melanocyte, which intermittently produces melanin either in a cyclic manner or as a periodic supply from a stem population. These three types of melanocytes synthesize melanin granules by an identical bipartite system. However, the control mechanism regulating the specific differentiation and postmelanin synthesis function of these cell types needs to be addressed in future research.

Glaucoma associated with a high number of mast cells in the uveal tract of an African lion cub

An 8-week-old male lion cub (Panthera leo) was referred for evaluation of an enlarged and reddened left eye. Ocular examination revealed a buphthalmic left globe, with corneal edema, superficial neovascularization, moderate episcleral injection, a fixed dilated pupil, and an intraocular pressure of greater than 41.5 mm of Hg as measured by the Schiotz tonometer and a human conversion chart. A diagnosis of glaucoma was made. A silicone prosthesis was implanted after evisceration of the intraocular contents. Histologic examination of the eviscerated uveal tissue revealed numerous congested and dilated vessels of various sizes. Neutrophils were marginated along the vascular endothelium, and the uveal stroma was infiltrated by a few lymphocytes and numbers (3 to 30/hpf) of widely disseminated, well-differentiated mast cells with abundant, well-granulated cytoplasm.

Theophylline effects on normal uveal melanocytes in culture: an ultrastructural study

Theophylline enhances maturation and differentiation of uveal melanocytes. By electron microscopy, we showed that theophylline changes small, dendritic melanocytes into large, platelike cells; it also enhances DOPA reaction as evidenced by increased deposition of DOPA reaction products in dilated cisternae and vesicles around the Golgi region. The effect is partially reversible in choroidal melanocytes but irreversible in iridial cells. It appears that theophylline, in addition to inducing tyrosine activity, accelerates the maturation and/or aging that normally occurs in cultured melanocytes when incubation is prolonged.

Normal uveal melanocytes in culture

Normal uveal melanocytes of rhesus and cynomolgus macaques can be grown in culture for 3-9 months and subcultured a few times. Postnatal and adult choroidal melanocytes are terminally differentiated cells. They are melanin-containing but not actively melanin-synthesizing cells. They do not undergo cell division, nor do they incorporate tritiated thymidine, but otherwise they are metabolically active. Postnatal and young adult iridial melanocytes are metabolically more active than choroidal cells. They require a feeder cell layer for attachment and to be maintained in a healthy condition. An endothelial cell line established from a rhesus fetal choroid-retina proves to be an effective feeder layer for adult iridial cells. Fetal uveal melanocytes divide slowly and usually require some stimulus and a special culture environment supplemented with 12-O-tetradecanolphorbol-13-acetate and cholera toxin. They can grow and differentiate in vitro. Iridial melanocytes grow and change into cells resembling postnatal choroidal melanocytes. Similar changes occur during development in utero. These findings further suggest that, in vivo, iridial melanocytes migrate and mature to become choroidal melanocytes.

Ocular immunization of guinea pigs

The experiments described were undertaken to determine which cells of guinea pigs immunized by different ocular routes produce the IgG1 and IgG2 antibodies detected in the serum. Guinea pigs were immunized intravitreally, topically, or by intravitreal immunization followed by topical conjunctival challenge. An indirect plaque assay was used to detect antibody producing cells in the cervical lymph nodes and ocular tissues. Passive hemagglutination, passive cutaneous anaphylaxis and ELISA assays were used to detect serum antibody. Both the topical and intravitreal methods initiated a primary antibody response. The guinea pigs developed IgG1 and IgG2 serum antibodies, but IgE and IgA antibodies were not detected. IgG1 and IgG2 plaque forming cells (PFC) were found in the lymph node and uveal tissues of the intravitreally immunized guinea pigs, and in the lymph node and conjunctival tissues of the topically immunized animals. IgA plaque forming cells were not detected in topically immunized animals. No antibody producing cells were found in intravitreally immunized guinea pigs sacrificed after the first conjunctival challenge (two months after sensitization). The highest numbers of lymph node and conjunctival PFC were found in the animals sacrificed three days after the second or third topical challenge. The numbers of IgG1 antibody producing cells in this group of guinea pigs were usually higher than the numbers of IgG2 PFC. Serum antibody levels, undetectable before challenge, increased after the second challenge. We conclude that both lymph node and ocular cells produce antibody in guinea pigs immunized by ocular routes.

Vasoactive intestinal polypeptide and the ocular innervation

The indirect immunofluorescence technique with antisera to vasoactive intestinal polypeptide (VIP) stains peripheral nerve fibers in both the anterior segment and the posterior segment of rat, guinea pig, cat, and rhesus monkey eyes. While immunoreactive corneal nerves are lacking, all four species have a prominent innervation of the superficial limbal blood vessels. The aqueous humor outflow apparatus of the rat, guinea pig, and cat, but not the monkey, contain VIP-like immunoreactive nerves. All four animals have immunoreactive iris nerve fibers, tending either to surround large blood vessels or to lie as free stromal nerves. Only in the cat are immunoreactive nerve fibers seen within the iris muscles. A modest number of VIP-like immunoreactive nerves are present in the ciliary body of all four animals; immunoreactive nerve fibers within the ciliary processes occur only in the rat and guinea pig. VIP-like immunoreactive nerves are found in the choroid of all four animals. An association of immunoreactive nerve fibers to uveal melanocytes also is apparent. The present findings expand several prior immunohistochemical studies of mammalian eyes in which the VIP-like immunoreactive nerves to the choroid was emphasized.

Absence of degenerative changes in retinal and uveal capillary pericytes in diabetic rats

Ultrastructural morphometric techniques were used to quantify pericyte degeneration in retinal and uveal capillaries of streptozotocin-diabetic rats in order to assess the suitability of this small rodent model of diabetes for studies of the pathogenesis of microvascular eye disease in diabetic humans. Male, Sprague-Dawley rats were killed by intraaortic perfusion of fixative 6 and 9 mos after induction of diabetes with 50 mg/kg streptozotocin. No differences were evident between diabetics and age-matched controls in capillary circumference, numbers of endothelial cells per capillary, and capillary cytoplasmic area of retinal, choroidal, and iridial vessels. Capillary basement membrane width and the percentage of the capillary circumference covered by pericytes were increased in retinas of diabetic vs age-matched control rats after 9 mos of diabetes (P less than 0.05), but no differences were evident in the number of pericyte processes per capillary and the percentage of vessels with pericyte nuclei. No differences in pericyte distributions were observed between control and diabetic rats in the choriocapillaris and iris after 9 mos of diabetes. These findings indicate that retinal capillary basement membrane thickening precedes any evidence of pericyte degenerative changes and suggest that pericyte degeneration analogous to that associated with human diabetic microangiopathy does not occur in this experimental animal model.

Pericyte form and distribution in rat retinal and uveal capillaries

Ultrastructural morphometric techniques were used to assess differences in endothelial cells and in pericyte structure and distribution in rat retinal and uveal capillaries. Retinal capillaries were significantly smaller than those in the three different uveal vascular beds, all of which were similar in size. Approximately 10% of the capillaries in the retina and choroid were formed by three endothelial cells, compared with 30% and 46% of capillaries sampled from ciliary processes and iris, respectively. The percentage of the capillary circumference covered by pericytes (46-58%) and the percentage of capillary sections with pericyte nuclei (12-16%) were similar in retina, iris, and ciliary processes. Corresponding data for the choriocapillaris indicated that pericyte coverage of these capillaries was approximately 50% of that observed in the other eye microcirculations. The number of pericyte processes per capillary varied markedly in the different vasculatures, with an average of three for capillaries in the retina and choriocapillaris and nine to eleven for capillaries in the iris and ciliary processes. These marked differences in capillary dimensions are consistent with the well-known capillary hemodynamic and functional differences of these tissues; however, the significance of the differences in pericyte shape, frequency and distribution in the different vasculatures of the eye is less clear.

Theophylline and melanocyte-stimulating hormone: effects on uveal melanocytes of adult rhesus eyes

The effects of theophylline and melanocyte-stimulating hormone (MSH) on cultured uveal melanocytes from the eyes of normal adult rhesus macaques were studied by light and electron microscopy and by dopa cytochemistry. The principal effects were changes in melanosome ultrastructure and an increased complexity of Golgi-associated vesicles and cisternae filled with dopa reaction products. The changes were more extensive in iris cells and less remarkable in choroid cells. The effects of theophylline were more pronounced than those of MSH. Our data suggest that normal iridial melanocytes, as do melanogenic murine melanoma cells, respond to theophylline or MSH by increasing tyrosinase synthesis, tyrosinase transfer, and melanization.

Total iridectomy in the primate in vivo: surgical technique and postoperative anatomy

A simple, brief surgical procedure for in vivo removal of the entire primate iris is described. A small peripheral corneal incision is made, and the prolapsed iris is torn from its insertion by forceps, without intraocular instrumentation. The eye recovers quickly and, except for the aniridia, the clinical and histologic appearance of the anterior segment is essentially normal. Experimental uses for the aniridic monkey eye are noted.

Effect of local corticosteroids on antibody-forming cells in the eye and draining lymph nodes

Significant numbers of antibody-forming cells (AFC) have been found in the cornea, uveal tract, and draining lymph nodes after the intracorneal injection of bovine gamma-globulin (BGG). To study the effect of locally administered corticosteroids on these antibody-forming tissues, we made unilateral intracorneal injections of rabbit eyes with BGG. These we followed immediately with subconjunctival injections of 10 mg. of triamcinolone suspension, and then with a second round of 10 mg. injections seven days later. A control group of animals received the BGG injections followed by two subconjunctival saline injections. We killed the animals on postinjection days 6, 9, 12, 15, and 21, and tested the draining lymph nodes, homolateral uveal tissue, and homolateral cornea for AFC by a modification of the Jerne placque technique. The local steroids had no effect on the number of AFC produced in the draining lymph nodes or on the circulating antibody response, but they reduced the number of AFC in the homolateral uveal tracts and corneas. Clinically there was less inflammatory response in the steroid-treated eyes than in the control eyes. The possible mechanisms by which corticosteroids achieve their anti-immunologic and anti-inflammatory benefits are discussed.